This invention relates to a sanding tool which is particularly but not exclusively designed for use with a settible filler material for example in body repair work on motor vehicles.
In body repair work, in order to obtain a smooth surface for finishing, any dents or depressions are filled with a settible body filler which is usually a mixture of a filling material and a hardener whereby the material sets hard after a predetermined period of time generally in the order of 5 to 10 minutes. For many years the conventional technique for finishing this material after it has been spread into the depression or dent has employed initially a cheese-grater device which shaves off an upper layer of the material so as to shape it initially generally to the required contours. The cheese-grater device can only be used on the material while it is hardening and hence is in a semi-moist state. Subsequent to the initial shaping, the material is sanded using generally 40 grade sandpaper which smooths the repair down to a smooth and properly contoured shape for painting and finishing. The painting and finishing steps often involve a first layer of primer followed by a putty glaze which is then sanded to remove any scratch marks from the initial rough sanding of the filler material. Finally the finished repair is painted using conventional techniques.
The sandpaper must be continually replaced since it tends to clog with the removed material and of course it rapidly wears. Large quantities of sandpaper are therefore consumed in a commercial process where body repair is carried out on a regular basis. Furthermore the sandpaper has a number of problems in that it develops dust which fills the atmosphere and of course is unsatisfactory from an health and environment point of view. In addition, the sandpaper can only be used when the filler material has effectively set hard since otherwise it rapidly clogs and becomes ineffective after a few strokes. This is disadvantageous because it creates the dust and in addition the material is much more difficult to work.
Despite the large expense of the continual replacement of sandpaper and the many disadvantages of this technique, this has been the only method available for body repair work and has been used exclusively for many years without the devlopment of suitable tools.
In addition, the sanding of other various materials is often necessary in various repairing and construction processes, the materials including wood, painted wood, fibre reinforced resin materials and plaster, all of which in many cases need to be sanded to provide a smooth finish or to remove undesired layers.